The present invention relates to a setting head and to a method for the insertion of elements consisting of head and shaft parts into pre-apertured workpieces, and is concerned, above all, but not exclusively, with the insertion of bolt elements into sheet metal parts, with the bolt elements being secured to the sheet metal parts via a riveted connection. Such rivetable bolt elements are known and can be classified into two different categories depending on whether the riveted connection arises in the region of the transition between the shaft and the head part or at the end face of the head facing away from the shaft part.
The present invention is concerned principally with the setting of bolt elements of the first named category in which the riveted connection arises in the region of the transition between the shaft part and the head part. However, it can be modified so that it can be used for bolts of the second category. The setting head is however in principle also suitable for the introduction or for the setting of hollow fastener elements such as rivetable nuts, above all when these have an elongated shape.
An example for a modern rivetable bolt which can be inserted into a sheet metal part or into a plate part by means of the setting head of the invention, or by means of the method of the invention, can be found in the German patent application P 44 20 475.8 of the present Applicants filed on Mar. 25th 1994. The element which is claimed there and which can be inserted into a sheet metal part comprises a shaft part and a unitary head part formed thereon and is characterized in that the element has concave peripherally closed fields or pockets at its underside serving as the contact surface, with the fields or pockets being partly bounded by ribs which extend outwardly away from the shaft part. The shaft side ends of the ribs extend in raised form along the shaft part and merge at their ends remote from the head part into at least one recess which is spirally arranged around the shaft part. During the setting process the metal of the sheet metal part is deformed into the fields and into the recess. This results in a form-fitted connection between the element and the sheet metal part. In this way, not only a rotational security of the element is present but also a connection which prevents the loss of the element from the sheet metal part prior to and during the mounting of the counter-element which has to be secured by the element to the sheet metal part.
Setting heads for the insertion of fastener elements onto bolt elements are, likewise, known and are frequently inserted into presses in order to rivet the fastening elements with sheet metal parts during the manufacture or shaping of the sheet metal parts.
By way of example a setting head can be found in DE-PS 34 47 006 which is suitable for the insertion of bolt elements which are riveted to the sheet metal part at the end face of the head facing away from the shaft part. In this respect the threaded part of the bolt is received over its full length within a bore of the plunger so that a high quality alignment of the bolt element is ensured as a result of the excellent mechanical guidance of the plunger.
The problem of ensuring a precise alignment of the bolt element within the setting head and during the insertion of the bolt element exists above all with bolt elements which are riveted to sheet metal parts in the region of the transition between the shaft part and the underside of the bolt head.